Inverted mixed latex for water flooding

ABSTRACT

An improved water flooding process for recovering oil from a subterranean oil-bearing formation which comprises introducing a stable liquid dispersion of a water-soluble anionic vinyl addition polymer and a water-soluble cationic polymer into an input well penetrating the formation. The dispersion comprises: A. A polymeric latex composed of a water-in-oil emulsion which contains dispersed therein a finely divided water-soluble anionic vinyl addition polymer, said polymeric latex having uniformly distributed therethroughout; and B. A water-soluble cationic polymer; WITH THE WEIGHT RATIO OF A:B being within the range of 1:10 to 10:1 and the total amount of A+B present within said dispersion being within the range of from 0.001 percent to 75 percent by weight.

' nited'States Patent [1 1 Dec. 25, 1973 Bott [ INVERTED MIXED LATEX FORWATER FLOODING [75] Inventor: Lawrence L. Bott, Oak Park, Ill.

[73] Assignee: Nalco Chemical Company, Chicago,

Ill.

[22] Filed: Jan. 31, 1972 [21] Appl. No.: 222,302

[52] [1.8. CI 166/275, 166/305 R, 252/855 D [51] Int. Cl E2lb 43/16 [58]Field of Search 166/271, 275, 276,

[56] References Cited UNITED STATES PATENTS 2,356,254 8/1944 Blair, Jr.et a]. 166/305 R 2,800,962 7 1957 Garst 252/855 D 2,816,610 12/1957Fisher. 252/855 D 2,851,105 9/1958 Garst 252/855 D 2,958,665 11/1960Stefcik et a1 252/855 D 3,416,601 12/1968 Young et a1. 3,540,532 11/1970Davis, Jr. et a1 166/275 Primary Examiner-Marvin A. Champion AssistantExaminer-Jack E. Ebel Attorney.lohn G. Premo et al.

[57] ABSTRACT An improved water flooding process for recovering oil froma subterranean oil-bearing formation which comprises introducing astable liquid dispersion of a watersoluble anionic vinyl additionpolymer and a watersoluble cationic polymer into an input wellpenetrating the formation. The dispersion comprises:

A. A polymeric latex composed of a water-in-oi] emulsion which containsdispersed therein a finely divided water-soluble anionic vinyl additionpolymer, said polymeric latex having uniformly distributedtherethroughout; and

B. A water-soluble cationic polymer;

with the weight ratio of AB being within the range of 1:10 to 10:1 andthe total amount of A+B present within said dispersion being within therange of from 0.001 percent to 75 percent by weight.

7 Claims, No Drawings 1 INVERTED MIXED LATEX FOR WATER FLOODING Thisinvention relates to the secondary recovery of petroleum fromsubterranean formations, and in particular concerns an improved waterflooding process.

The technique of water flooding to recover oil from so-called depletedreservoirs is well known. It is described in detail in U. S. Pat. No.2,827,964. In general, such process consists of introducing an aqueousmedium into one or more'injection wells which penetrate the depletedformation, and forcing such mediumthrough the formation toward one ormore production wells which likewise penetrate the formation. In thesocalled five-spot drive, the aqueous medium is forced down fourinjection wells which are more or less symetrically located around aproducing well. As the flooding medium passes through the formation itdisplaces the residual oil therein and carries it into the producingwell from which it is recovered by conventional means. In order toinsure that the flooding medium advances through the formation to theproduction well with a more or less plane front rather than in the formof fingers extending through the strata of highest permeability) it hasbeen proposed that the viscosity of at least the forward portion of theflooding medium be adjusted so as to be of the order of, or greaterthan, that of the oil to be recovered. This has been accomplished byadding a viscosity-increasing agent to at least the initial portion ofthe flooding medium. Fatty acid soaps, alginates, sucrose, glycerine,carboxymethylcellulose and water-soluble polymers such as polyvinyl andpolyallyl alcohols have been suggested for use as such agents in aqueousflooding media. Certain of such agents, however, precipitate fromsolution when exposed to typical reservoir temperatures and/or to theanionis or cations normally present in subterranean formations, whereasothers must be employed in very large amounts to secure the desiredincrease in viscosity.

Other materials for increasing the viscosity of the flooding medium havebeen used. Specifically, watersoluble polymers have been dissolvedto-increase the viscosity of the flooding medium. For example, thewatersoluble partially hydrolyzed acrylamide polymers have been inwidespread use as well as the alkyl esters of acrylic and methacrylicacids, methacrylamide, styrene, vinyl acetate, acrylonitrile,methacrylonitrile, vinyl alkyl ethers, vinyl chloride, vinylidenechloride, etc.

Serous drawbacks have been experienced with these polymers in that theyhave quite slow dissolution times; some as long as one hour.Furthermore, as the flooding medium is forced further along in theformation, it tends to become diluted by water which is found throughoutthe formation. In addition, the viscosityincreasing additives tend to belost through adsorpoion on the reservoir rock surface. As a result ofthis dilution, the blocking or plugging ability of the flooding mediumis diminished until at some point in the formation the flooding mediumhas been so diluted that it no I longer blocks the channels at all.

The present invention is based upon the discovery that a stable liquiddispersion of a water-soluble anionic vinyl addition polymer and awater-soluble cationic polymer can be injected into an input well whichpenetrates the formation, and forcing the water-in-oil emulsion throughthe formation toward at least one producing well penetrating theformation at a distance from the input well. This phenomenon is due tothe fact that the stable liquid dispersion containing the watersolubleanionic vinyl addition polymer and watersoluble cationic polymer iscapable of being inverted in water whereby the anionic vinyl additionpolymer instantly reacts with the cationic polymer to produce a gel-likestructure. This gel-like structure permeates throughout the subterraneanformation.

The consequences of this procedure will cause increased producedoil-to-water ratios for a certain volume of water sent through thesubterranean formation. Thus, the total amount of water needed to besent through the formation will be reduced.

OBJECTS It is an object of this invention to increase the oil-towaterratio in the secondary recovery of oil from subterranean formations.

It is also an object of this invention to provide a stable liquiddispersion of a water-soluble anionic vinyl addition polymer and awater-soluble cationic polymer, which stable liquid dispersion iscapable of being inverted in water whereby the anionic vinyl additionpolymer instantly reacts with the cationic polymer to produce a gel-likestructure for recovering petroleum from a subterranean oil-bearingformation.

Further objects will appear hereinafter.

THE INVENTION This invention relates to a process for recovering oilfrom a subterranean oil-bearing formation which comprises introducing astable liquid dispersion of a watersoluble anionic vinyl additionpolymer and a watersoluble cationic polymer into an input well whichpenetrates the formation, and forcing the stable liquid dispersionthrough the formation toward at least one producing well penetrating theformation at a distance from the input well.

The stable liquid dispersion is characterized as capable of beinginverted in water and the anionic vinyl addition polymer instantlyreacts with the cationic polymer to produce a reaction product which maybe described as a three-dimensional water and hydrocarbon liquidinsoluble gel-like structure.

As mentioned above, the stable liquid dispersion is pumped into theinput well. Once in the formation and upon contact with the water in theformation, the stable liquid dispersion is inverted and the polymersreact as described above to form the gel-like structure. This structureis by nature oleophilic, and resists passage of aqueous fluids butpromotes oil flow through the treated formation.

The stable liquid dispersion is generally used by diluting a dispersionconcentrate with an organic liquid. The dispersion concentrate is awater-soluble anionic vinyl addition polymer in the form of awater-in-oil emulsion which contains dispersed therein thefinely-divided water-soluble anionic vinyl addition polymer. Thisdispersion concentrate contains uniformly distributed there-throughout awater-soluble cationic polymer. The water-soluble anionic vinyl additionpolymers that are used in the practice of the invention may beillustrated by the following list of polymers:

TABLE I Number Name I Polyacrylic acid-sodium salt The above polymersmay vary in molecular weight. They may be as low as 10,000 or as high as12,000.000 or more. In many of the more useful applications, which willbe more fully discussed hereafter, the molecular weight will be greaterthan 1,000,000.

The invention contemplates using as preferred watersoluble anionic vinyladdition polymers the homoand copolymers of acrylic acid as well as thewater-soluble salts thereof.

THE WATER-SOLUBLE CATIONIC POLYMERS These polymers also may be selectedfrom a wide variety of known polymeric materials. Several of thesepolymers are listed below in TABLE II.

TABLE II Number Name I Ethylene dichloride-ammonia condensation polymers2 Tetracthylenc pentaminc-cpichlorohydrin condensation polymersEpichlorohydrin-ammonia condensation polymers Polyethylene imineEthylene diamine Polydiallyl amine Dimethylamino ethyl methacrylate Themethyl chloride quaternary of Number I The benzol chloride quaternary ofNumber 7 Guanidine formaldehyde condensation polymers.AcryIamidc-diallylamine (30%) The above polymers are illustrative oftypical watersoluble cationic polymeric materials that may be used inthe practices of the invention. A preferred class of these polymers maybe described as alkylene polyamines which are illustrated by polymers 1,2, 3, 4, and 8 above.

Many of the above polymers have been described with respect to thereactants from which they are prepared. A detailed discussion of theabove polymers and other cationic polymers appears in Canadian Pat. No.731,212, the disclosure of which is incorporated herein by reference.The polymers may be employed as solutions or in the form of awater-in-oil latex emulsion. When the polymers are of the vinyl additiontype they may be copolymers of other ethylenically saturated monomers.Such copolymers should contain at least 5 percent by weight of thecationic monomer.

THE ANIONIC VINYL ADDITION POLYMER POLYMERIC LATEX The inventioncontemplates utilizing the watersoluble anionic vinyl addition polymersin the form of water-in-oil emulsion which contains dispersed thereinthe water-soluble anionic vinyl addition polymer.

Emulsions of this type are prepared by dispersing the anionic vinyladdition polymer into a water-in-oil emulsion. These polymers asproduced by most manufacturing processes are in the form of powders orlump-like agglomerates of varying particle size. It is desirable thatthe particles, before being placed into the emulsion, be comminuted bygrinding, abrading or the like so that their average particle size isless than 5 millimeters and preferably is within the range of l to 5microns. After the powders have been comminuted, they may be dispersedinto the water-in-oil emulsion by means of agitation provided by suchdevices as stirrers, shakers and the like. To be commercially practical,the amount of polymer in the emulsion should be at least 2 percent byweight. The invention contemplates using emulsions containing between 5to percent by weight with preferred emulsions having a polymerconcentration within the range of 10 to 45 percent by weight. In somecases the starting emulsions are converted to suspensions due to thenature and the amount of the polymer present therein.

From a commercial standpoint it is beneficial that the polymer emulsionsthus described be stable, yet at the same time contain relatively largeamounts of polymers. One method of insuring that the polymers do notprecipitate when dispersed in the emulsion is that the particle size ofthe polymer be as small as possible. Thus polymers dispersed in theemulsifiers are quite stable when the particle size is within the rangeof 5 millimicrons up to about 5 microns. To produce particle sizeswithin these limitations, spray dryers with appropriate size nozzles maybe used. It also is possible to prepare the polymer-containing emulsionof the watersoluble vinyl addition polymers directly from the vinylmonomers from which these polymers are synthesized. Suchpolymer-containing emulsions may be synthesized by using thewater-in-oil emulsion polymerization technique set forth in U. S. Pat.No. 3,284,393. The teachings of this patent comprises forming awater-inoil emulsion of water-soluble ethylenic unsaturated monomers.The emulsion is formed by utilizing a waterin-oil emulsifying agent. Tothis monomer is added a free radical-type polymerization catalyst andthe heat is applied under free radical-forming conditions to formwater-soluble polymer latices. The polymeric latices produced by thispatent are relatively unstable and frequently must be treated withadditional emulsifiers to render the products stable.

The water-in-oil emulsions used to prepare the above polymers may beformulated by any number of known techniques.

The oils used in preparing these emulsions may be selected from a largegroup of organic liquids which include liquid hydrocarbons andsubstituted liquid hydrocarbons.

A preferred group of organic liquids are the hydrocarbon liquids whichinclude both aromatic and aliphatic compounds. Thus, such organichydrocarbon liquids as benzene, xylene; toluene, mineral oils,kerosenes, naphthas and, in certain instances, petrolatums may be used.A particularly useful oil from the standpoint of its physical andchemical properties is the branch-chain isoparaffinic solvent sold byHumble Oil and Refining Company under the Tradename ISO- PAR M." Typicalspecifications of this narrow cut isoparaffinic solvent are set forthbelow in TABLE III.

TABLE III Specification Properties Mimimum Maximum Test Method 160.0'ASTM D 93 The amount of oil used in relation to the water to preparethe emulsion may be varied over wide ranges. As a general rule, theamount of oil-to-water may vary between Szl to 1:10 with preferableemulsions being prepared in the ratio of 1:2 to 1:10. These ratios areillustrative of emulsions that can be prepared, although it should beunderstood that the invention is not limited thereby.

soluble cationic polymers are in the form of aqueous solutions whichcontain 5 to 40 percent by weight of the polymer and are added to thepolymeric latex. Alternatively, they may be nearly water-free. Afteruniformly mixing the two components there results a dispersionconcentrate of a water-soluble anionic vinyl addition polymer and awater-soluble cationic polymer. The proportions of the two polymers maybe varied to a considerable degree. For instance, the ratio of thewater-soluble anionic vinyl addition polymer to watersoluble cationicpolymer may vary between 1:10 to 10:1 on a weight basis. A preferredratio is 1:5 to 5:1. The most preferred ratio is 1:2 to 2:1.

The amount of the water-soluble vinyl addition polymers plus thewater-soluble cationic polymers present' in the finished dispersionconcentrate may be varied over a wide range of concentrations, e.g.,dispersion concentrates containing from 0.001 percent to 75 percent byweight are useful, although for most applica- The emulsions may beprepared by any number of tions the total weight of the two polymerscontained in techniques. For example, the emulsions may be prepared byusing high speed agitation or ultrasonic tech niques. In most instances,however, it is desirable that the emulsion be a stable emulsion and toachieve this end it is often necessary to employ an oil solubleemulsifying agent. The amount of emulsifying agent to pro-,

vide an emulsion will have to be determined by routine experimentation.As a general rule it may be said that the amount of oil solubleemulsifier may range from 0.1 to 30 percent by weight based on theweight of the oil. To produce stable emulsions the amount of emulsifierwill normally be within the range of 12 to 20 percent by weight of theoil.

Rather than provide a listing of suitable emulsifiers,

the dispersion concentrate will be within the range of 5 percent topercent by weight, with a very beneficial dispersion being one whichcontains between 10 to 30 percent by weight of the two polymers.

The finished dispersion concentrates are stable at room temperature forperiods of time ranging between several days to as long as six monthssince they may be prepared over a wide variety of concentrations.Dispersion concentrates containing large amounts of polymers may beprepared and shipped to a use point and then diluted with an organicliquid just prior to use.

To illustrate the preparation of dispersion concentrates, a variety ofemulsions were prepared containing different water soluble anionic vinyladdition polymers.

recommended as being i aq y r the d 35 These emulsions are set forthbelow in TABLE IV.

low HLB materials which are well documented in the literature and aresummarized in the Atlas HLB Surfactant Selector. Although theseemulsifiers are useful in producing good water-in-oil emulsions, othersurfactants may be used as long as they are capable of producing theseemulsions. For instance, we have found that certain high HLB surfactantsare capable of producing stable water-in-oil emulsions. A typical lowHLB emulsifier is sorbitan monooleate.

PREPRATION OF THE DISPERSION CONCENTRATE Once the latices containing thewater-soluble anionic vinyl addition polymers are prepared, thedispersion concentrate is prepared by combining them with thewater-soluble cationic polymers by the utilization of conventionalmixing techniques. Preferably, the water- DISPERSION CONCENTRATE A Toemulsion in TABLE IV, COMPOSITION NUM- BER VI, there was added 30percent by weight of an aqueous dispersion containing 23 percent byweight of an alkylene polyamine prepared from the condensation ofethylene dichloride and ammonia. The polymer was prepared using thetechniques set forth in Canadian Pat. No. 785,829.

DISPERSION CONCENTRATE B To COMPOSITION NUMBER VI in TABLE IV, there wasadded an aqueous dispersion which contained 25 percent by weight of anammonia ethylene dichloride polymer of the type used in DISPERSION Aabove, with the exception it had been quaternized with methyl chloride.

To illustrate other novel dispersion concentrates of V the inventionTABLE V is presented below:

TABLE V Anionic Latex Table IV C l Disper- SlON by Weight 60 by CationicPolymer Weight 20% solution of a tetraethylene pentamine epichlorohydrinreaction product (Canadian Pat.

731,212) Ethylene diamine 70 75 acrylamide, 25

dimethylamino ethyl methacrylate copolymer in the form of a latex(watcr-in-oil) See TABLE II, U. S. 3,624,0[9

THE ORGANIC LIQUID Generally, the dispersion concentrate will be dilutedwith an organic liquid just prior to use. As mentioned above, thepreferred dispersion concentrate will have from to 40 percent by weightof the two polymers. In this application, the dispersion concentratewill be diluted with the organic liquid so that the stable liquiddispersion will have 0.001 to 10 percent by weight of the two polymers.

The dispersion concentrate can be diluted with the organic liquid(including crude oil) near the location of the well where it is to beused. This on-site dilution procedure may be performed in a mixing tanknear the well location and-then be pumped directly into the well. Theorganic liquids of this invention include both aromatic and aliphatichydrocarbon compounds. Thus, such organic hydrocarbon liquids asbenzene, xylene, toluene, mineral oils, kerosene, naphthas andpetroleums may be used. In particular, the petroleum recovered from theprimary recovery operation (crude oil) may be used to dilute thedispersion concentrate for use. The use of petroleum obtained from theprimary recovery operation eliminates the burdensome problems inhandling other organic liquids but also results in a great decrease incost.

Oftentimes it is desirable to use a more concentrated flooding mediumthan the ones as defined above. If such is the case, the dispersionconcentrate may be used without dilution with an organic liquid. If suchis the case the polymeric latex concentrate would be pumped directlyinto the well without any type of dilution.

lNVERSlONS OF THE STABLE LIQUID DISPERSION One of the most interestingphenomenon that occurs in working with the above described anioniclatices is the fact that under certain conditions the emulsion, whichcontains dispersed therein the finely divided water-soluble anionicvinyl addition polymers, may be inverted.

The water-soluble anionic vinyl addition polymercontaining emulsions maybe inverted by any number of means. The most convenient resides in theuse of a surfactant.

The surfactant may be combined with the stable liquid dispersion .byseveral different techniques. It may be added and mixed with the stableliquid dispersion just prior to being pumped into the subterraneanformation. The placement of a surfactant into the stable liquiddispersion causes it to more rapidly invert and release the polymer andform the gel-like structure. When this technique is used to invert theflooding medium the amount of surfactant present in the water may varyover a range of from 0.01 to 10 percent based on polymer.

Secondly, the surfactant may be introduced as a solution into thesubterranean formation prior to the injection of the stable liquiddispersion. The surfactant may be diluted with a brine which wasrecovered and separated from primary recovery processes. This brinesolution is readily available at little or no cost. The surfactant isadded to the brine solution in a concentration of from 0.5 to 5.0percent by weight. When the crude oil containing the stable liquiddispersion is contacted with the brine containing surfactant in thesubterranean formation the emulsion is inverted and the anionic vinyladdition polymer instantly reacts with the cationic polymer to produce agel-like structure. The rate at which this occurs may be controlled bythe type and amount of emulsifier used to prepare the polymer system.The polymer-containing emulsions release the polymer in water after aperiod of time in such a manner as to avoid the dissolution problem ofthe prior art. Thus, when the water-in-oil emulsion is pumped into aninput well it will mix with water in the subterranean formation at whichtime the polymer will be released forming a gel-like structure.

It is preferred that once the crude oil containing the emulsion isintroduced into the formation that the emulsion be left static for from5 to 72 hours. This period of time has been found to be sufficient tocompletely invert the emulsion and release the watersoluble vinyladdition polymer into solution. As mentioned above, this time may varywith the composition as well as the rock formation. Thus, it is possiblefor complete dissolution to occur either more rapidly or more slowlythan the preferred time range. It should be stressed that the inventionis not limited by the amount of time necessary to dissolve the polymer.

The process comprises the following steps:

A. Introducing a brine solution containing from 0.5 to 5.0 percent byweight of a surfactant into an input well which penetrates saidformation; then,

B. Introducing a stable liquid dispersion into said input well whichpenetrates said formation, and allowing the stable liquid dispersion tobe left static for from 5 to 72 hours; said dispersion containing:

1. a polymeric latex composed of a water-in-oil emulsion which containsdispersed therein a finely divided water-soluble anionic vinyl additionpolymer, said polymeric latex having uniformly distributedtherethroughout; and

2. a water-soluble cationic polymer:

with the weight ratio of A:B being within the range of 1:10 to 10:1 andthe total amount of A+B present within said dispersion being within therange of from 0.001 percent to 75 percent by weight, then forcing saiddispersion through said formation toward at least one producing wellpenetrating said formation at a dis- Other surfactants that may be85511325356685 soaps such as sodium and potassium myristate, laurate,palmitate, oleate, stearate, resinate, and hydroabietate,

the alkali metal alkyl or alkylene sulfates, such as so-' dium laurylsulfate, potassium stearyl sulfate, the alkali metal alkyl or alkylenesulfonates, such as sodium lau ryl sulfonate, potassium stearylsulfonate, and sodium cetyl sulfonate, sulfonated mineral oil, as wellas the ammonium salts thereof; and salts of higher means like laurylamine hydrochloride, and stearyl amine hydrobromide.

Any anionic, cationic or nonionic compound can be used as thesurfactant.

In addition to using the water soluble surfactants described above,other surfactants may be used such as silicones, clays and the likewhich are included as surfactants since, in certain instances, they tendto invert the emulsion even though they are not water-soluble.

In other specific cases the surfactant may be directly added to thepolymer-containing emulsion; thereby rendering it self-inverting uponcontact with water. These products, while capable of being used incertain systems, must be carefully formulated since the surfactants maytend to interact with the emulsifier or the emulsion and destroy itprior to its being used.

The emulsions may be inverted by treating them with aqueous solutions ofalkaline materials such as solutions of sodium hydroxide, ammonia,amines, sodium aluminate or the like.

Other techniques for inverting the emulsions include the use ofagitation, high voltage electrical fields, heat and pH shift, as well asthe placement into the water, into which the polymer-containing emulsionis to be dissolved, certain electrolytes. For any particularpolymer-containing emulsion a suitable method for its inversion may bereadily determined by routine experimentation.

THE GEL-LIKE STRUCTURES When the stable liquid dispersions are thusinverted the anionic vinyl addition polymer instantly reacts with thecationic polymer to produce within a matter of minutes a reactionproduct which may be described as a three-dimensional, water andhydrocarbon liquid insoluble gel-like structure, which is composed ofwhat is believed to be ionically combined intimate admixture of the twopolymers. These gel-like structures are spongy, porous, and aresubstantially incapable of adherence to most hydrophobic surfaces.

EXAMPLES When the stable liquid dispersions are injected into inputwells they have a high water-to-oil output ratio, generally resultingfrom many years of secondary recovery operations, it is possible togreatly improve the amount of oil produced in relation to the waterrecovered.

For instance, when the stable liquid dispersions would be used to treattypical produced fluid from, for instance a West Texas water floodingfield, improvements in the amount of oil produced will range frombetween 20 to as high as 40 percent by weight.

Specifically, when the stable liquid dispersions of the invention areused typical results that would be obtained are set forth in Table VIbelow. Typical of the dilutions used are injection fluid which iscomposed of 97 percent crude oil, 4 percent water, 1 percent polymer.

The results shown in Table VI would be obtained on dispersionconcentrates A through E, as described above, after continuous injectionwould be made into the producing wells over a 1 to 5 week period.

TABLE VI Increase in oil com- Disper- Concen- Organic pared to Ex. sionContrate by Organic Liquid by dry No. centrate weight Liquid WeightPolymer l A 5 Crude Oil 95 35 2 B 10 Crude Oil 90 20 3 C 3 Crude Oil 972| 4 D 5 Crude Oil 95 40 5 E 5 Crude Oil 95 38 I claim:

1. A process for recovering oil from a subterranean oilbearing formationwhich comprises introducing a stable liquid dispersion of awater-soluble anionic vinyl addition polymer and a water-solublecationic polymer in the presence of a water-soluble surfactant into aninput well penetrating said formation and forcing said stable liquiddispersion through said formation and toward at least one producing wellpenetrating said formation at a distance from said input well, and saiddispersion is inverted by means of a surfactant, said stable liquiddispersion comprising:

A. a polymeric latex composed of a water-in-oil emulsion which containsdispersed therein a finelydivided water-soluble anionic vinyl additionpolymer;

B. said pOlymeric latex having uniformly dispersed therethroughout awater-soluble cationic polymer; with a weight ratio of A18 being withinthe range of 1:10 to 10:1 and total amount of A+B present within saiddispersion being within the range of from 0.001 percent to 75 percent byweight.

2. A process for recovering oil from a subterranean oil-bearingformation which comprises introducing a stable liquid dispersion of awater-soluble anionic vinyl addition polymer and a water-solublecationic polymer in the presence of a water-soluble surfactant into aninput well penetrating said formation and forcing said stable liquiddispersion through said formation and toward at least one producing wellpenetrating said formation at a distance from said input well, saidstable iiquid dispersion comprising:

A. a polymeric latex composed of a water-in-oil emulsion which containsdispersed therein a finely divided water-soluble anionic vinyl additionpolymer;

B. said polymeric latex having uniformly dispersed therethroughout awater-soluble cationic polymer; with a weight ratio of AB being withinthe range of 1:10 to 10:1 and total amount of A+B present within saiddispersion being within the range from 0.001 percent to percent byweight.

3. The process of claim 1 where the stable liquid dispersion iscomprised of:

A. a polymeric latex composed of a water-in-oil emulsion which containsdispersed therein a finely divided polyacrylic acid or a water-solublesalt thereof;

B. said polymeric latex having uniformly dispersed therethroughout awater-soluble alkylene polyamine polymer; with a weight ratio of A:Bbeing withinthe range of 1:10 to 10:1 and the total of A+B presentwithin said dispersion being within the range of from 0.001 percent to75 percent by weight.

4. The process of claim 1 where the water-soluble anionic polymer ispolyacrylic acid or its water-soluble salts and the water-solublecationic polymer is an alkylene polyamine polymer.

5. The process of claim 1 wherein the stable liquid dispersion has aweight ratio of A:B within the range of from 1:5 to 5:1 and the amountof A+B present within said dispersion is within the range of 5 percentto 40 percent by weight.

6. The process of claim 1 wherein the stable liquid dispersion has aweight ratio of A:B within the range of from 1:2 to 2:1 and the amountof A+B present within said dispersion is within the range of frompercent emulsion which contains dispersed therein a finely dividedwater-soluble anionic vinyl addition polymer;

2. said polymeric latex having uniformly dispersed therethroughout awater-soluble cationic polymer; with a weight ratio of A:B being withinthe range of 1:10 to 10:1 and total amount of A+B present within saiddispersion being within the range of from 0.001 percent to percent byweight.

2. A process for recovering oil from a subterranean oil-bearingformation which comprises introducing a stable liquid dispersion of awater-soluble anionic vinyl addition polymer and a water-solublecationic polymer in the presence of a water-soluble surfactant into aninput well penetrating said formation and forcing said stable liquiddispersion through said formation and toward at least one producing wellpenetrating said formation at a distance from said input well, saidstable iiquid dispersion comprising: A. a polymeric latex composed of awater-in-oil emulsion which contains dispersed therein a finely dividedwater-soluble anionic vinyl addition polymer; B. said polymeric latexhaving uniformly dispersed therethroughout a water-soluble cationicpolymer; with a weight ratio of A:B being within the range of 1:10 to10:1 and total amount of A+B present within said dispersion being withinthe range from 0.001 percent to 75 percent by weight.
 2. said polymericlatex having uniformly dispersed therethroughout a water-solublecationic polymer; with a weight ratio of A:B being within the range of1:10 to 10:1 and total amount of A+B present within said dispersionbeing within the range of from 0.001 percent to 75 percent by weight. 3.The process of claim 1 where the stable liquid dispersion is comprisedof: A. a polymeric latex composed of a water-in-oil emulsion whichcontains dispersed therein a finely divided polyacrylic acid or awater-soluble salt thereof; B. said polymeric latex having uniformlydispersed therethroughout a water-soluble alkylene polyamine polymer;with a weight ratio of A:B being within the range of 1:10 to 10:1 andthe total of A+B present within said dispersion being within the rangeof from 0.001 percent to 75 percent by weight.
 4. The process of claim 1where the water-soluble anionic polymer is polyacrylic acid or itswater-soluble salts and the water-soluble cationic polymer is analkylene polyamine polymer.
 5. The process of claim 1 wherein the stableliquid dispersion has a weight ratio of A:B within the range of from 1:5to 5:1 and the amount of A+B present within said dispersion is withinthe range of 5 percent to 40 percent by weight.
 6. The process of claim1 wherein the stable liquid dispersion has a weight ratio of A:B withinthe range of from 1:2 to 2:1 and the amount of A+B present within saiddispersion is within the range of from 10 percent to 30 percent byweight.
 7. A process for recovering oil from a subterranean oil-bearingformation which comprises the following steps: A. introducing a brinesolution containing from 0.5 to 5.0 percent by weight of a surfactantinto an input well which penetrates said formation; then, B. introducinga stable liquid dispersion into said input well which penetrates sAidformation and allowing the stable liquid dispersion to be left staticfor from 5 to 72 hours; said dispersion comprising: